How has nobody really mentioned the Renji and Rukia possibility?
They have a wonderful dynamic together and a lot of history from growing up together. Rukia fell for Kaien after being parted from Renji, and i always felt this was her replacing her affection on somebody similiar to Renji (subject to opinion of course).
I believe Renji is definitely in love with Rukia, but Rukia still needs to get over her part in Kaiens death before she can move on. I really hope these two get together, more so than any other two in Bleach, because the way they clash yet are so in tune with one another depicts an adorable relationship
